This invention relates to a catheter for controllably obstructing the flow in a vein and more particularly to such a catheter having ports on either side of the obstruction for measuring the differential pressure therebetween as a measure of the degree of the obstruction obtained.
When surgery is performed on a patient in the supine (horizontal) position, which is done in the vast majority of cases, air embolism is not possible because pressure within the veins is greater than atmospheric pressure. For the supine patient, open veins bleed. However, when the patient is positioned in the sitting upright position, the pressure in the veins of the head and neck become negative in relation to atmospheric pressure, and those veins, if cut, readily draw in air. Air inside the circulatory system induces circulatory failure and poor pulmonary oxygenation, and a large embolus may induce the early demise of a patient.
Surgery in the upright position is a highly desirable condition sought by surgeons for certain types of operations including brain surgery, but the high probability of air aspiration into cut veins discourages and curtails this practice. Air embolism is a dreadful insidious condition which may totally overshadow gains obtained by performing surgery in the sitting position. Air embolism can successfully be detected, but treatment, while surgery is in progress can be a nightmare. Air embolism produces a frothy blood-air mixture which is difficult to aspirate and attempts at air removal are often fruitless, too late and lead to disastrous consequences.
It is therefore an object of this invention to provide a method for preventing air aspiration into cut veins and consequent air embolism during surgery of the head and neck of the patient in the sitting position, without adversely affecting the patient's normal physiology.
It is a further object of this invention to provide a catheter insertable into the patient's superior cava vein that includes a means for controllable partial obstruction of the superior cava vein and a means for measuring the differential venous blood pressure on either side of the blockage to guide blockage control.